1. Field of the Invention
This invention relates to a method for improving the texture and/or flavor characteristics of certain proteinaceous materials such as yeasts or vegetable flours. More particularly it relates to a gaseous treatment with anhydrous ammonia vapor.
2. Description of the Prior Art
Flavor and texture improvement are two areas which receive continual attention in the food industry. In the case of soy flour, for example, a nagging problem facing users is the "beany" taste which limits the amounts of soy which can be incorporated into a food product without detracting from the product's flavor acceptability. Similarly, dried yeast also has a flavor problem, although to a lesser extent. In addition, dried yeast lacks sufficient textural strength to be used in certain foods in large quantities. Such yeast products typically disperse into single cells when contacted with water, and as such can impart a "mushy" texture to the product into which they are incorporated.
Flavor modification treatments for microorganisms have been developed using liquid solvents for flavor extraction. As an example, U.S. Pat. No. 3,615,654 (1971) to Ayukawa et al., teaches a liquid ammonia extraction of microbial cells at temperatures below the boiling point of liquid ammonia (-33.4.degree. C.) for the purpose of improving flavor, color, odor, and taste of the microbial cell product, as well as reducing the ribonucleic acid content. After extraction the treated cells are separated from the liquid ammonia by conventional methods and recovered.
It has now been discovered that this solid-liquid separation step can be eliminated by the process of the invention, which utilizes a gaseous ammonia treatment. The gaseous ammonia treatment of this invention not only improves the flavor of proteinaceous materials, but also quite unexpectedly improves the texturization properties of yeasts.